Inertial measurement devices, such as gyroscopes and accelerometers, provide high-precision sensing, however, historically, their cost, size, and power requirements have prevented their widespread use in industries such as consumer products, gaming devices, automobiles, and handheld positioning systems.
More recently, micro-electro-mechanical systems (MEMS) devices, such as gyroscopes and accelerometers, have been gaining increased attention from multiple industries since micro-machining technologies have made fabrication of miniature gyroscopes and accelerometers possible. Miniaturization also enables integration of MEMS devices with readout electronics on the same die, resulting in reduced size, cost, and power consumption as well as improved resolution by reducing noise. Consumer products such as digital cameras, 3D gaming equipment, and automotive sensors are employing MEMS devices because of their numerous advantages. The demand for low cost, more sophisticated, and user-friendly devices by the consumers has caused a steep rise in the demand of MEMS sensors, as they offer adequate reliability and performance at very low prices.
State-of-the-art MEMS devices, such as those disclosed in U.S. Pat. Nos. 7,578,189; 7,892,876; 8,173,470; 8,372,67; 8,528,404; 7,543,496; and 8,166,816, are able to sense rotational (i.e. angle or angular velocity of rotation around an axis) or translational motion (i.e. linear acceleration along an axis) around and along axes. Techniques for manufacturing such devices using a process known as High Aspect Ratio Poly and Single Silicon (HARPSS) are disclosed in U.S. Pat. No. 7,023,065 entitled Capacitive Resonators and Methods of Fabrication by Ayazi, et al., and other publications.
The current monolithic HARPSS fabrication process requires significantly complex and difficult process steps to create all the features necessary for a multi-axis gyro and accelerometer sensor.
Accordingly, need exists for an improved manufacturing process which to eliminates the most costly and difficult elements in the manufacturing process.
A further need exists for an improved manufacturing process that enables device manufacturing costs to be lowered to a point that would be competitive for high volume consumer electronics products.
In addition, semiconductor manufacturing, especially microelectronics, utilize Silicon On Insulator (SOI) technology, i.e. the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates to provide an selectively removable material layer (i.e. SiO2) below the mechanical device layer (i.e. Si) in order to fabricate a movable micro-mechanical element. However, such as SOI technology increases the cost and complexity of the semiconductor device manufacturing process.
Accordingly, need exists for an improved MEMS device manufacturing process which eliminates the need to utilize SOI manufacturing techniques while providing the same or better device yield and performance.